If the State Department complies, it could push the final decision on Keystone past 2016, meaning it would be passed from President Barack Obama -- who's widely expected to reject the project -- to his successor.
On Tuesday, the Obama administration said it was still reviewing TransCanada's request, which came in the form of a letter addressed to Secretary of State John Kerry. Officials said as the State Department works to decipher the appeal, the Keystone review would continue.
White House press secretary Josh Earnest, speaking at the daily briefing, cast skepticism on the TransCanada's intentions.
"This is a process that has taken an extensive amount of time to complete," he said. "Given how long it's taken, it seems unusual to me to suggest that somehow it should be paused yet again."
In a statement Monday, TransCanada said it would be "appropriate" for Kerry to suspend the current review of the Keystone proposal as Nebraska's public service commission deliberates over the pipeline's route.
The company said it could take up to 12 months for the Nebraska process to be completed, adding further delay to an approval process that's already taken seven years.
Ahead of TransCanada's announcement, the White House said Monday it expected Obama to make a final determination on Keystone before he leaves office, though wouldn't specify whether that meant this year or next.
Earnest said the company's request to halt the review process has not changed that timeline.
Most pro-Keystone advocates have largely resigned themselves to a rejection from the White House, given Obama's past statements casting skepticism that the project would create enough jobs to outweigh the potential environmental risks.
Proponents say the pipeline, which would carry oil from the tar sands of Alberta to the Gulf of Mexico, would advance energy independence in North America.
But environmentalists say the risks of leaks and spills are too great, and say the project would only deepen dependence on fossil fuels.
After TransCanada's statement, anti-Keystone groups cast the decision as a last-ditch ploy to avoid what appears would be an unfavorable decision on the pipeline.
"After nearly seven years of trying to force the President's hand to approve the Keystone XL pipeline, TransCanada is now desperately trying to block President Obama from even making a decision at all," Elijah Zarlin, director of the CREDO Climate Campaigns, said in a statement. "This is yet another victory for the overwhelming grassroots opposition along the route and across the country."